The present invention relates to a new tire rasp hub assembly for use in tire buffing machines. More particularly, it relates to a novel tire rasp hub assembly which incorporates nonplanar or "bent" spacers with nonplanar or "bent" rasp blades.
The disclosures of U.S. Pat. Nos. 5,033,175, 4,019,234 and 2,703,446 are incorporated herein by reference into this application.
Tire buffing machines are well known in the tire retreading industry. Conventionally, a tire buffing machine includes both a structure for mounting a used tire and a rasp hub which removes the worn tread from the used tire prior to the retreading process. The used tire is rotated while it is held against the rapidly rotating rasp hub whose outside perimeter is provided with a multitude of tire rasp blades. When so engaged against the used tire, the rasp blades cut or shear small segments of rubber from the worn tread surface area of the tire. In this way, the tire is "buffed" to remove the unwanted used tread and to achieve an evenly textured surface suitable for retreading.
Tire rasp blades, together with intervening spacers, are assembled on the periphery of the rasp hub between the hub front and back plates. U.S. Pat. Nos. 2,703,446 and 4,019,234 disclose such conventional prior art rasp hub assemblies wherein the back plate of the hub has axially directed support pins for mounting the rasp blades and spacers. The front plate is then placed on the support pins against the assembled blades and spacers and locked into place.
Use of bent tire rasp blades with flat spacers is described in U.S. Pat. No. 5,033,175. This arrangement creates a circumferentially interlocked hub with less potential for mechanical failure at high rotational speeds. The tire buffing machine hub assembly disclosed in U.S. Pat. No. 5,033,175 has proven generally satisfactory. However, in this assembly two separate planar spacers are associated with and overlap each rasp blade. A one-for-one correspondence and positioning of spacers and blades, together with a spacer configuration which facilitates the proper location of the blades, would allow the hub assembly to be assembled more quickly and easily. Additionally, conventional rasp hub assemblies (as shown, for example, in FIG. 9), do not allow the use of an odd number of the bent blades disclosed in U.S. Pat. No. 5,033,175 with a conventional hub, since conventional hubs employ only an even number of alternate angled surfaces or sections and each such blade covers two angled surfaces.
Finally, there is a continuing need to improve tire rasp performance while maintaining or reducing power requirements. Thus, designers recognize that a superior rasp hub assembly would provide enhanced control, superior cutting, durability and buffing action, a safe, stable hub assembly, and an economical hub design which can be assembled and maintained by lesser skilled workers. The present invention accomplishes each of these goals.